1. Field of the Invention
The present invention relates generally to sealing arrangement for use in the entry/exit ports of cable enclosures and, in particular, to sealing members configured to seal around looped cables as they pass though the entry/exit ports of cable enclosures.
2. State of the Art
Telecommunication cables are commonly used for the transmission of data across networks. Although some of these cables may be electrically conductive, fibre optic cables are generally preferred across large distances due to their enhanced bandwidth capabilities and their immunity to electromagnetic and radiomagnetic interference.
Networks are constructed from the conjunction of many cables. At various points along the network, a cable may be opened up (or ‘spliced’) so as to join it to another cable, perhaps to distribute data or power to a different location or new recipient. Thus, branches are commonly added to networks by splicing existing cables and making new connections.
At each branching point in the network, the spliced cable becomes exposed and is vulnerable to the ingress of moisture, dirt, insects or other environmental hazards. These hazards can degrade the performance of the cable, and thus some form of protection is required. It is common to use some type of enclosure to protect the cable(s) at these vulnerable points.
The prior art discloses known enclosures for electrical and optical fibre cables, including enclosures which permit the insertion of one or more cables and protect some form of cable connection (either a splice, a connector or other connection device). Such enclosures are also used to house surplus lengths of cable which may be stored for future use. It is common for such cables to be looped and subsequently stored inside such enclosures with a view to splicing the cable off so as to service new destinations or branches.
Typically, such cable enclosures feature one or more openings (known as ‘ports’) through which the cables can be fed for entry or exit purposes. Hereinafter, the phrase ‘entry port’, or simply the term ‘port’, may be taken to mean a port which permits the entry and/or exit of a cable or a plurality of cables. Unless appropriately sealed, such ports provide an entrance for environmental hazards such as moisture, dirt and insects and thus jeopardise the performance of the cable. Therefore, the port needs to be sealed with the use of a bung or grommet such that entry/exit of the cable(s) is still permitted while maintaining the integrity of the cable where exposed inside the enclosure.
A variety of enclosure seals are known in the prior art, including the use of heat shrink sleeving, self-vulcanising tapes, gels, potting compounds and so forth. One common type of seal is a pre-formed grommet which permits the passage of the cable(s) and is subsequently inserted into the port, forming an air/moisture tight blockade. However, the cable is usually inserted into the grommet by passing it though the body of the seal into a cavity via a slit made in the grommet wall. In order to prevent the ingress of environmental hazards, the split must be subsequently sealed. This is commonly achieved using the application of some type of mastic or gel tape installed under compression, but such an application is highly craft sensitive. If the application is performed incorrectly, the seal will degrade and the cable may become exposed to leakage and interference and, ultimately, degradation. The skill of the technician installing the grommet is therefore vital to the successful performance of the grommet.
Furthermore, the simultaneous or subsequent application of an additional sealing tape or compound requires the use of additional materials and tools, and lengthens the installation process considerably.
Further still, health and safety factors become relevant when applying heat shrink or resins to the seal, which would preferably be avoided.
Further still, it is not uncommon for optical fibres to break or become damaged during the installation process. However, the application of heat shrink, resin or tape makes it difficult to re-use the enclosure seal with an unspoilt cable in the event of such damage.